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Gauge Field Emergence from Kalb-Ramond Localization

A new mechanism, valid for any smooth version of the Randall-Sundrum model, of getting localized massless vector field on the brane is described here. This is obtained by dimensional reduction of a five dimension massive two form, or Kalb-Ramond field, giving a Kalb-Ramond and an emergent vector field in four dimensions. A geometrical coupling with the Ricci scalar is proposed and the coupling constant is fixed such that the components of the fields are localized. The solution is obtained by decomposing the fields in transversal and longitudinal parts and showing that this give decoupled equations of motion for the transverse vector and KR fields in four dimensions. We also prove some identities satisfied by the transverse components of the fields. With this is possible to fix the coupling constant in a way that a localized zero mode for both components on the brane is obtained. Then, all the above results are generalized to the massive $p-$form field. It is also shown that in general an effective $p$ and $(p-1)-$forms can not be localized on the brane and we have to sort one of them to localize. Therefore, we can not have a vector and a scalar field localized by dimensional reduction of the five dimensional vector field. In fact we find the expression $p=(d-1)/2$ which determines what forms will give rise to both fields localized. For $D=5$, as expected, this is valid only for the KR field.Comment: Improved version. Some factors corrected and definitions added. The main results continue vali

New Analytical Solutions for Bosonic Field Trapping in Thick Branes

New analytical solutions for gravity, scalar and vector field localization in Randall-Sundrum(RS) models are found. A smooth version of the warp factor with an associated function $f(z)=\exp(3A(z)/2)$ inside the walls ($|z|<d$) is defined, leading to an associated equation and physical constraints on the continuity and smoothness of the background resulting in a new space of analytical solutions. We solve this associated equation analytically for the parabolic and P\"oschl-Teller potentials and analyze the spectrum of resonances for these fields. By using the boundary conditions we are able to show that, for any of these solutions, the density probability for finding a massive mode in the membrane has a universal behavior for small values of mass given by $|\psi_m(0)|^2=\beta_1m+\beta_3m^3+\beta_L m^3\log(m)+\cdots$. As a consequence, the form of the leading order correction, for example, to the Newton's law is general and does not depend on the potential used. At the end we also discuss why complications arises when we try to use the method to find analytical solutions to the fermion case.Comment: 11 pages, 4 figures; v2: extended version; references and section added; title, conclusions and abstract change

Avaliação preliminar da viabilidade do consórcio de ovinos com fruteiras.

A possibilidade de associar a criação de ovinos à produção de fruteiras tem sido alvo de crescente interesse, especialmente nas áreas irrigadas do vale do São Francisco. Estudo em vários países indicam boas perspectivas para este tipo de associação pelo seu grande potencial em reduzir os custos de produção das fruteiras. Com esse objetivo, a Embrapa conduziu três ensaios preliminares na região Nordeste. O primeiro, consorciando ovinos com coqueirais da Baixada Litorânea de Sergipe, o segundo, com o cultivo de mangueiras Tommy Atkins, em latossolos irrigados do município de Curaçá, BA e o terceiro, com videiras irrigadas, no município de Petrolina, PE. Essas avaliações consideraram parâmetros de produtividade e de comportamento animal, de eficiência no controle da vegetação espontânea e de produtividade das fruteiras. Em todos os ensaios, os resultados observados indicam as boas perspectivas do sistema em controlar as ervas daninhas, reduzindo ou eliminando roçagens mecânicas, capinas manuais e aplicações de herbicidas, sem afetar a produtividade das fruteiras e de, adicionalmente, obter, na forma de produção de carne ovina, uma receita adicional ao empreendimento

Gauge/string duality and scalar glueball mass ratios

It has been shown by Polchinski and Strassler that the scaling of high energy QCD scattering amplitudes can be obtained from string theory. They considered an AdS slice as an approximation for the dual space of a confining gauge theory. Here we use this approximation to estimate in a very simple way the ratios of scalar glueball masses imposing Dirichlet boundary conditions on the string dilaton field. These ratios are in good agreement with the results in the literature. We also find that they do not depend on the size of the slice.Comment: 5 pages, no figures. References updated. Version published in JHE